JP3392888B2 - Selective growth of layers containing aluminum. - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to methods of making gallium arsenide semiconductor devices, and more particularly to selective growth of layers containing aluminum such as aluminum gallium arsenide.

[0002]

BACKGROUND OF THE INVENTION Due to the features of high speed and direct forbidden zones,
Gallium arsenide devices promise a great deal when used in high speed electronics, optical devices and integrated circuits. Such devices typically include multiple layers of gallium arsenide and aluminum gallium arsenide, which are doped to the n- or p-type conductivity, semiconductor electronic devices such as bipolar or field effect transistors, or photodetectors. Device or an optical device such as a surface emitting laser.

A preferred method of making a gallium arsenide layer structure is by GJ Davis et al., Chemtronics 3 (1988).
Organometallic molecular beam epitaxy (MOM
Molecular beam epitaxy like the process of BE).
For other molecular beam processes, see WT Tsang's Journal of Electronics Materials.
cs Materials ), page 235 (1986).

In summary, the molecular beam process involves placing a substrate in a low pressure growth chamber, heating the substrate and directing a molecular beam of gas molecules onto the substrate that decomposes to form the desired layer.
The process called MBE is typically a group III,
While only a source of elements and dopant elements are used for Group V, the MONBE process uses a compound gas source that supplies various elements and at least one Group III or dopant element. A typical MOMBE process used to fabricate pnp and npn transistors is described in the pending patent, C.R. Abernath, both filed February 28, 1991.
y) et al., application numbers 07/662549 and 07/662
550.

One unfavorable feature of prior art molecular beam processes is that during the growth of aluminum gallium arsenide,
Using arsine (AsH ₃ ) or arsenic as the source. Many device fabrication schemes require selective regrowth of aluminum gallium arsenide layers in the unmasked, confined areas of the masked substrate. At the desired low temperatures ( < 600 ° C.), regrowth with arsine or arsenic will be non-selective and will grow on the mask as well as on the unmasked substrate.

Efforts to achieve selective AlGaAs growth have also met with limited success.
As or As ₂ adheres to the mask surface and serves as a catalyst for decomposition of the Al precursor. A growth temperature above 600 ° C. is required to prevent nucleation of Al-containing material on the mask surface. However, lower temperature growth is desirable for the fabrication of many electronic devices. Therefore, there is a need for an improved method of selectively growing a layer containing aluminum.

[0007]

SUMMARY OF THE INVENTION Aluminum containing layers are grown by a molecular beam process using arsenic precursor phenylarsine (PhAs). Since PhAs is more active than arsine and less active than arsenic, it is III-V
It decomposes selectively on the surface but not on the mask material. Therefore, unlike conventional processes, growth with PhAs selectively grows on unmasked gallium arsenide, but prevents growth on typical mask materials such as silicon nitride. It

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 shows a deposition step of a layer containing aluminum, and FIGS. 2 and 3 show cross sections of a typical sample before and after the deposition process of FIG.

As shown in FIG. 1A, the first step is the preparation of a sample 10 including a substrate 9 having a surface layer 13 of a gallium arsenide group III-V semiconductor.

As shown in FIG. 2, the sample 10 is a mask layer 1 of a non-III-V material such as silicon nitride that exposes only predetermined regions 12 of the semiconductor layer 13.
1 may be included. Such a sample is mask 11
It may be the result of several previous steps to produce the desired stack of differently doped semiconductor layers (not shown), which may also be in the region below and below layer 13. The semiconductor may be any material of the gallium arsenide family including gallium arsenide, aluminum gallium arsenide, indium gallium arsenide, aluminum arsenide, aluminum indium arsenide or aluminum indium phosphide.

The next step, shown in FIG. 1B, is to heat the sample in an evacuated container that can be referred to as the growth chamber. Sample 10 is Intevac, Gas source, Ge
placed in the growth chamber such as nII, evacuated to less than 10- ₄ torr pressure, 600 ° C. or less of the temperature, preferably heated to 500 ° -550 ° C.. The exposed as-formed semiconductor surface is essentially free of impurities such as residual oxides, and it is advantageous that the surface be thoroughly cleaned according to techniques well known to those skilled in the art.

As shown in FIG. 1C, the next step is to expose the semiconductor surface to gas molecules of phenylarsine and at the same time to a gas precursor containing aluminum, such as trimethylamine alane (TMAAl). Here, the desired aluminum-containing material is A
With lGaAs, the surface should be exposed to a gas precursor containing gallium such as trimethylgallium (TMG). Phenylarsine is available from Air Products and Chemicals, Allentown, PA. Preferably, all precursors are introduced into the growth chamber through H2 carrier gas directed onto the substrate at a flow rate in the range of 0.1-20 SCCM. Selective epitaxial growth of aluminum gallium arsenide is obtained on semiconductor surfaces at rates on the order of 95 Å / min.

The resulting structure is schematically depicted in FIG. As can be seen, the growth layer 14 is the semiconductor layer 13
It is selectively formed on the mask layer 11 and is not formed on the mask layer 11. If desired, mask layer 11 can be selectively removed by dissolving silicon nitride in hot phosphoric acid. This process with PhAs has many advantages over the prior art with arsine as the arsenic precursor. PhAs has a wider growth temperature range than arsine,
Enables selective growth. In particular, it enables selective growth at low temperatures ( < 600 ° C.), which is desirable for the fabrication of semiconductor electronic and optical devices.

PhAs is particularly useful for the selective growth of p-type layers of aluminum gallium arsenide. This is because the inclusion of carbon, which is a p-type dopant for aluminum gallium arsenide, is not excluded. The result of this effect can be seen with reference to FIG. This figure is a plot of the concentration of various elements with respect to the depth of layers successively grown using various precursors. As shown, growth with triethylgallium (TEG), trimethylamine alane (TMAAl) and arsenic yielded carbon levels of about 5 × 10 16 cm -3. On the other hand, when the same group III flux was combined with phenylarsine, the carbon content was about 1.8 × 10 18 cm -3.
Increased.

FIG. 5 is a schematic diagram of a gallium arsenide device in the form of an "emitter-up" pnp transistor that can be advantageously made using the method of the present invention. The device 40 depicted in FIG. 5 comprises a substrate 41 supporting a sequentially grown layer 42 acting as a transistor subcollector, a collector 4
3, including a base region 44 consisting of layers 45, 46 and 47. It is convenient to describe layer 46 as a functional base layer,
It involves enveloping layers 45 and 47 which act as spacer regions (in some experts the entire region 44 may be referred to as the base region). The emitter layer 48 is then followed by an optional layer 49, and finally by layers 50 and 51, the three layers constituting the emitter contact region.

Table 1 below details the process used to create this major layer of the device of FIG. DM
AAA refers to tri-dimethylamino arsenide, and as to the method of using DMAA to form a gallium arsenide layer, the applicant's pending patent “Gallium-Containing Layer Selective Growth Method Co-filed concurrently with this case” ”.

[0017]

[Table 1]

[Brief description of drawings]

FIG. 1 shows a step of growing a layer containing aluminum.
It is a figure shown with a block diagram.

FIG. 2 is a schematic cross-sectional view of a typical sample on which a layer of aluminum gallium arsenide can be grown.

FIG. 3 shows the sample of FIG. 2 after growth.

FIG. 4 is a diagram showing a graph of measured concentration against depth when various precursors are used.

FIG. 5 is a schematic diagram of a preferred electronic device.

[Explanation of symbols]

9 substrates 10 samples 11 Mask layer 12 areas 13 Surface layer, semiconductor layer, layer 14 Growth layer 40 devices 41 substrate 42 layers 43 collector 44 Base area, area 45,46,47 layers 48 Emitter layer 49,50,51 layers

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Stephen John Pearton United States 07901 New Jersey, Summit, Euclid Avenue 19-Apartment 3 (72) Inventor Van Ren United States 07059 New Jersey, Warren, Berkshire Drive 13 ( 72) Inventor Patrick William Whisk United States 08812 New Jersey, Greenbrook, Gold Street 19 (56) References JP-A-2-229721 (JP, A) JP-A-3-3319 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21 / 203,21 / 205 H01L 21 / 363,21 / 365

Claims (5)

(57) [Claims] 1. Preparing a masked sample comprising an unmasked surface portion of a gallium arsenide group III-V semiconductor, heating the sample in a depressurized container, and the unmasked surface portion. Selection of an aluminum-containing material layer on the sample comprising exposing the sample to a gaseous aluminum precursor containing trimethylamine alane and phenylarsine to selectively grow an aluminum-containing material thereon. Growth method. 2. The method according to claim 1, wherein the sample is heated to a temperature in the range of 500 ° C. to 600 ° C. 3. Preparing a material further comprising a surface layer of a gallium arsenide group III-V semiconductor material and a mask layer that covers a portion of the surface layer and exposes selected portions of the surface layer; Inside, the material is 500 ℃ ~ 600 ℃
A gas aluminum precursor containing tritylamine alane so as to selectively grow a layer of aluminum gallium arsenide on the selected portion of the surface region; A method of growing an aluminum gallium arsenide layer on a sample comprising exposing to a gaseous gallium precursor and phenylarsine. 4. The method of claim 3, wherein the gallium precursor comprises trimethylgallium. 5. The method of claim 1, wherein the mask is silicon nitride.